1. Field of the invention
This invention relates to a novel optical disc of a small diameter and a large capacity. More particularly, it relates to an optical disc device employing the optical disc.
2. Related Art
Large-capacity data, such as that for a still picture or a moving picture, is stored on a recording medium, such as an optical disc, and is random-accessed and reproduced whenever so required.
The optical disc can be random-accessed, and is higher in recording density than the magnetic recording medium, such as a so-called floppy disc, while data can be rewritten if the disc is a magneto-optical disc. Therefore, the optical disc is suited for storage of the large-capacity data.
Recently, a demand is raised for increasing the capacity of the optical disc further, such that, in view of ease in handling, development of a small-sized optical disc of a large capacity is incumbent.
As the small-sized optical disc, there is known a magneto-optical disc 64 mm in diameter, that is a so-called mini-disc (MD), while there has also been proposed so-called MD data for recording digital information signals. However, the recording capacity cannot be raised beyond 140 MB.
This recording capacity of 140 Mb cannot be said to be sufficient.